Woodward The Swift valve is a sonic flow-metering valve

Description

The system is available in two primary configurations. The "Swift" configuration

provides either single- or dual-metering valves in a single housing. This

configuration can be integrated into a new or existing gas metering system to

provide low-cost, accurate, reliable control. The Swift Model 200 system, sizes

65. 36. and 20. have been designed to provide system mass flow accuracy of 2%

of point at 100% of rated flow across the entire temperature range. The Swift

Model 200 system, size 11. has been designed to provide system mass flow

accuracy of 6.2% of point between 50 and 100% of rated flow, across the entire

temperature range.

The Swift gas metering system components include one or two metering valves

and one valve driver (see Figure 1-1). For fuel systems requiring two

independently modulated fuel flows, the primary valve can be integrated with a

secondary metering valve. The primary valve can accommodate this integration

without duplicating either electrical or mechanical connections.

Swift Valve

The Swift valve is a sonic flow-metering valve. The valve has a

converging/diverging nozzle and a moving needle to adjust the valve flow area.

An open loop step motor through a rack and pinion drive positions the needle. A

return spring is included to remove the effects of gear backlash and to minimize

closed-valve leakage. A mechanical stop allows the valve to re-zero the valve

position during start-up. After the re-zero, the driver counts the step motor steps

and monitors the step motor position.

Swift Driver

The driver is effectively a positioner that will accept a desired position signal from

another device in the system, such as a speed control, and drive the valve to that

position. The position controller software is executed on dual Texas Instruments

16-bit DSPs, operating at 40 MHz, onboard the Swift Driver. The driver can be

commanded to a position via 4–20 mA, PWM, or CAN/DeviceNet interfaces. The

driver monitors all available signals, internal and external, and annunciates any

detected shutdown conditions through the discrete output. A discrete input is

available to remotely shut down the actuator and to reset shutdown conditions.

Features of the driver include dual (2) model-based position control loops, on-line

diagnostics, CAN communications, and service port communications (described

in detail in Chapter 5). A Windows-based Service Tool software program is

available for monitoring, troubleshooting, and parameter adjustments. The

Service Tool software is loaded on a PC and communicates serially to the driver

via RS-232. Refer to Chapter 7 (Service Tool) for installation instructions.